Spa skirt



FIG. 1 is a top perspective view of the ornamental design of a spa skirt;

FIG. 2 is a top view of the spa skirt;

FIG. 3 is a front view of the spa skirt;

FIG. 4 is a back view of the spa skirt;

FIG. 5 is a left side view of the spa skirt; and,

FIG. 6, is a right side view of the spa skirt.

The matter delineated in dashed lines forms no part of the claimed ornamental design. 

I claim the ornamental design for a spa skirt, as shown and described. 